To provide a polyolefin-based, flame-retardant fiber which is safe on a fire, can harmlessly be subjected to disposal treatments such as incineration, can be recycled, has the same performances, such as strength, as those of conventional fibers, and gives fiber products causing no trouble when used, and to provided a composition containing the fiber.

This fiber is characterized by adding 0.1 to 10 wt.% of a high mol.wt. hindered amine-based stabilizer as a flame-retardant effect agent to a 2 to 8C α-olefin homo- or co-polymer resin to impart flame retardancy to the olefin resin, and also a composition containing the fiber is provided.